Crystal structure of ytterbium copper stannides in the range 14-32 at.% tin

The crystal structures of four new intermetallic compounds of the Yb-Cu-Sn system were determined by X-ray diffraction on powders and single crystals and by optical and electron microscopy: Yb3.63Cu23.13Sn10.83 - hexagonal, P6/mmm, hP50-12.41, a=1195.7(2) pm, c=516.2(1) pm, R=0.022, 402 reflections, has a new structure with a disordered part localised in channels parallel to the six-fold axis and centred at the origin of the unit cell; YbCu9Sn4 - tetragonal, I4/mcm, tI56, a=861.7(1) pm, c=1239.2(2) pm, R=0.021, 325 reflections, is isotypic with LaFe9Si4, ordered ternary derivative of the cubic NaZn13 type; Yb7.2Cu10Sn8 - hexagonal, P63/mmc, hP26-0.8, a=453.0(1) pm, c=3042.3(5) pm, R=0.055, 233 reflections, and Yb14.4Cu18Sn15 - trigonal, R3¯m, hR48-0.6, a=451.9(1) pm, c=5664(1) pm, R=0.050, 263 reflections. The structures of the last two phases are built up by different stacking of the same units, taken from the GdPt2Sn and SrPtSb (ordered AlB2) types. In the Cu-rich alloys containing 10 to 28 at.% tin, compounds were found with the atomic arrangements of the orthorhombic CeCu5Au, Ce2Cu9Sn2.65 and hexagonal CeNi5Sn types